ABB RELION REX640 Technical Manual page 1082

Section 5
Protection related functions
1076
CCBRBRF is initiated by operating different protection functions or digital logics
inside the protection relay. It is also possible to initiate the function externally through
a binary input.
CCBRBRF can be blocked by using an internally assigned signal or an external signal
from a binary input. This signal blocks the function of the breaker failure protection
even when the timers have started or the timers are reset.
The retrip timer is initiated after the start input is set to true. When the pre-defined time
setting is exceeded, CCBRBRF issues the retrip and sends a trip command, for
example, to the circuit breaker's second trip coil. Both a retrip with current check and
an unconditional retrip are available. When a retrip with current check is chosen, the
retrip is performed only if there is a current flow through the circuit breaker.
The backup trip timer is also initiated at the same time as the retrip timer. If CCBRBRF
detects a failure in tripping the fault within the set backup delay time, which is longer
than the retrip time, it sends a backup trip signal to the chosen backup breakers. The
circuit breakers are normally upstream breakers which feed fault current to a faulty
feeder.
The backup trip always includes a current check criterion. This means that the
criterion for a breaker failure is that there is a current flow through the circuit breaker
after the set backup delay time.
REF 615
GUID-40F5E5B1-8ABD-4A5B-9974-765CCBCEDD56 V1 EN
Figure 578: Typical breaker failure protection scheme in distribution substations
1MRS759142 C
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Technical Manual
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REX640